Engine Performance problem
1996 GMC Jimmy 6 cyl Four Wheel Drive Automatic 257000 miles

My 1996 Jimmy surges. I got DTCs P0440 and P0507.I was told that this usually signifies a faulty oxygen sensor on the exhaust.There are three sensors on the exhaust,how do I test to see which one is bad?

10/21/08
Gentlemen,
I would like to thank SWilliams for his response to my question.I followed his advice about checking all my vacuum hoses from the purge solinoid and discovered that my pcvalve had split allowing a vacuum leak.I replaced the pcvalve and the problem is now corrected.Thank you again.

P0440 is EVAP System control system malfunction.
P0507 is Idle control system, Idle higher than expected.

Neither one has to do with the O2 sensors. What it does sound like is a failed EVAP purge solenoid on the engine. That is the control that opens to allow a vacuum to reach the fuel tank during the EVAP test. If it has failed open it will create a vacuum leak that also allows in fuel vapors. That would cause both codes.